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Cyber-resilience
Published in Stavros Shiaeles, Nicholas Kolokotronis, Internet of Things, Threats, Landscape, and Countermeasures, 2021
E. Bellini, G. Sargsyan, D. Kavallieros
Thus, applying a risk-based approach to a problem that requires a resilience-based solution, or vice versa, can lead to investment in systems that do not produce the effects that stakeholders expect. In particular, risk management considers effort to prevent or defuse threats before they occur, but whenever risks are identified and actions taken to reduce risk, there still remains residual risk. As such, resilience assessment and management are, in part, an effort to address that remaining known, but unmitigated, risk as well as enhance the overall ability of the system to respond to unknown or emerging threats. In other words, it represents the low-probability/high-impact events, sometimes called “fat-tail” events, that are difficult to account for and even harder to predict.
Nuclear power
Published in Peter N. Nemetz, Unsustainable World, 2022
A significant concern that has only recently emerged is referred to as a “fat-tail” distribution in risk analysis. While the probability of accidents may be low, there is a class of such risks—as demonstrated by the Chernobyl disaster—with truly catastrophic consequences. While an industrial accident at a fossil-fueled plant may endanger some workers and cause localized environmental pollution, a similar accident at a nuclear reactor can essentially remove a large swath of land—in the order of hundreds of square miles—from long-term cultivation and human habitation. It can also cause an increased number of cancers among the general public. Three of the most dangerous radionuclides released from nuclear reactor accidents include cesium-137, strontium-90, and iodine-131. The general rule of thumb within the nuclear safety community is that the public must be protected from these radioactive elements for ten to thirteen half-lives, where a half-life is the time it takes for the radioactive emissions from an isotope to fall by 50 percent from the previous level. The half-lives for these three isotopes are 30.0 years, 29.12 years, and 8.04 days respectively. This suggests that a geographic area seriously contaminated with these isotopes should remain off limits to human habitation for up to three hundred years. These qualitative and quantitative risks are unique to the nuclear power industry. It is somewhat ironic that the renewed interest in extreme nuclear events among governments, academics, and the general public is reminiscent of the early focus of WASH-740 on such occurrences, despite the shortcomings of that report from 1957.
Nonlinear Time Series Analysis
Published in Tucker S. McElroy, Dimitris N. Politis, Time Series, 2019
Tucker S. McElroy, Dimitris N. Politis
Remark 11.3.5. Fat Tails and Financial Data The second condition of Theorem 11.3.4 is sometimes violated, i.e., for some financial data, a finite fourth moment is not tenable. In fact, another characteristic of financial data, besides volatility clustering, is a slow rate of decay of the tails in the marginal PDF. Such a PDF is said to have fat tails. For example, a Student t distribution with 3 degrees of freedom has fat tails, and its fourth moment is infinite.
Decision making under deep uncertainty for adapting urban drainage systems to change
Published in Urban Water Journal, 2018
Filip Babovic, Ana Mijic, Kaveh Madani
In addition predictions of the probability distributions of future variables may have high variances and ‘fat tails’ (Taleb 2012). The presence of fat tails denotes a high probability of extreme events occurring. Given that the effectiveness of flood defence plans can deteriorate rapidly if small deviations occur from the projected climatic conditions, errors in prediction can lead to systems that deliver inadequate levels of flood protection. Traditional, optimised systems perform well across a narrow band of conditions. McInerney, Lempert, and Keller (2012, 549) noted that this was similar to ‘dancing on the top of a needle’, as such systems tend to experience very rapid declines in performance when conditions are outside of this narrow range of conditions.
A meso-scale gravel tracer model for large gravel-bed rivers
Published in Journal of Applied Water Engineering and Research, 2019
Michael Tritthart, Philipp Gmeiner, Marcel Liedermann, Helmut Habersack
In particular the log-normal distribution, however, tends to exhibit ‘fat tails’, i.e. relatively rare but extraordinarily high values. Since a large number of random numbers is drawn for a full particle path, such values are almost certain to occur. Hence a physical limit is imposed for both distributions, effectively enforcing ut to be smaller than the near-bed flow velocity magnitude. This is achieved by drawing a new random number if the resulting tracer velocity is too large.